Component testing for food allergies beneficial when additional specificity required
ATLANTA — Component testing for specific food allergies is most beneficial when current diagnostic testing is not adequately specific, according to a presentation at the American College of Allergy, Asthma and Immunology Annual Scientific Meeting.
“Our current diagnostic methods in food allergy are lacking … so we’re anxious to have new methods that will help that diagnostic specificity,” Robert A. Wood, MD, FACAAI, professor of pediatrics and international health, and director of pediatric allergy and immunology, Johns Hopkins University School of Medicine, told Healio Allergy/Immunology. “Component testing is one of those methods that has been developed over the last decade that is improving the diagnostic accuracy in a patient with suspected food allergy.
Robert A. Wood
“From a clinical standpoint, it’s really only ready for use for peanut allergy and in that, not all patients with peanut allergy really have to have component testing, but there’s a subset with suspected allergy where it is incredibly helpful to make a more clear diagnosis.”
Gallus domesticus (Gal d) 1, commonly known as ovomucoid, was the major allergen component as a severity marker for egg, Wood said. Measuring this generally was not helpful in predicting the outcome of baked egg challenges, he said.
In discussing cow’s milk allergy, Wood referenced bos domesticus (Bos d) 8 in the protein casein.
“From a statistical standpoint, there is value, but whether that patient … needs to have this test done prior to proceeding to the baked milk challenge is debatable, and we would proceed with the challenge, irrespective of the casein IgE,” he said.
Regarding the allergen component in soy, including glycine max (Gly m) 5 and 6, Wood said, “A third to half of patients that have true soy allergy will show specific antibody to Gly m 5 and Gly m 6.” Component testing might be beneficial in identifying patients who must avoid soy compared with those with less severe symptoms, he said.
The major wheat component of interest was triticium aestivum (Tri a) 19 or the omega-5-gliadin, which has been associated with a risk for IgE reaction. Component testing might distinguish a patient with “a less than perfectly clear history” as having a true wheat reactivity, Wood said.
“We hear mostly (about component testing) in regard to peanut,” he said.
“There are a number of different important peanut components,” including Ara h 1, 2 and 3, which are most often associated with “true peanut allergy,” Wood said, discussing studies related to Ara h 2, which has been best correlated with clinical reactivity.
“Component-based testing is not needed for most of our patients with peanut allergy,” he said. “Your patient who has had a clear reaction at age 18 months and a peanut IgE of 50 does not need a component test to prove they’re peanut allergic.”
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Disclosure: Wood reports no relevant financial disclosures.